Separation of asphaltenes and conversion of black oils

ABSTRACT

Removal of asphaltenes from a hydrocarbonaceous black oil is effected through the use of a foam chamber and a foam breaker. In one application, the asphaltene-free material is thermally cracked and the heavier portion of the cracked effluent is recycled to combine with the fresh feed. The foam is created through the use of high-pressure hydrogen, being intimately admixed with the black oil, followed by depressuring into a foam chamber.

United States Patent [72] Inventors Rog rs, Edward [56] References Citedgi a m k "5 both f m UNITED STATES PATENTS A I No :32 My 2,854,3989/1958 Knox 208/86 -3,281,350 10/1966 Codetetal. 208/86 F1led Dec. 17,1969 3,288,703 11/1966 Spars et a1. 208/86 Patented 3 362 901 1/1968Szepe et al 208/86 Assignee Universal Oil Products Company Des Plaines,Ill. Primary Examiner-Herbert Levine Attorneys.lames R. Hoatson, Jr. andRobert W. Erickson SEPARATION OF ASPHALTENES AND ABSTRACT: Removal ofasphaltenes from a hydrocar- VERSION OF BLACK OILS bonaceous black 011is effected through the use of a foam 1 D i F chamber and a foambreaker. In one application, the asphal- 5 C 8 raw tene-free material isthermally cracked and the heavier por- U.S. Cl 208/86, tion of thecracked effluent is recycled to combine with the 208/309 fresh feed. Thefoam is created through the use of high-pres- Int. Cl Cl0c 3/00 surehydrogen, being intimately admixed with the black oil, Field of Search208/86, 309 followed by depressuring into a foam chamber.

[4 1 Foam Breaker 8 4 Foam Chamber 7?. Hydrogen g /0 7 l f e 2 1 MixingZane l5 Thermal Gail Product SeparaI/an SEPARATION OF ASPHALTENES ANDCONVERSION OF BLACK OILS The process described herein is adaptable tothe removal of asphaltenes from petroleum crude oil residuals having ahigh metals content. More specifically, our invention is directed towardthe removal of asphaltenes from a hydrocarbonaceous black oil andconversion of the asphaltene-free material. This process is applicableto atmospheric tower bottoms, vacuum column bottoms, crude oil residuum,topped and/or reduced crude oils, coal oil extracts, crude oilsextracted from tar sands, etc., all of which are commonly referred to inthe art as black oils.

Petroleum crude oils, and particularly the heavy residuals obtainedtherefrom, contain sulfurous compounds in exceedingly large quantities,nitrogenous compounds, high molecular weight organometallic complexesprincipally comprising nickel and vanadium as the metallic component,and hydrocarboninsoluble asphaltic material. The latter is generallyfound to be complexed with sulfur, and to a certain extent, with themetallic contaminants. A black oil is generally characterized inpetroleum technology as a heavy hydrocarbonaceous material of which morethan about 10.0 percent (by volume) boils above a temperature of about1,050F. (referred to as nondistillables) and which further generally hasa gravity less than about 20.0API. Sulfur concentrations are exceedinglyhigh, most often greater than 2.0 percent by weight. Conradson carbonresidue factors exceed 1.0 percent by weight and the concentration ofmetals can range from as low as p.p.m. to as high as about 750 p.p.m.

The process encompassed by the present invention is particularlydirected toward the conversion of those black oils contaminated by ahigh asphaltene content. Specific examples of the charge stocks, towhich the present technique is adaptable, include a vacuum tower bottomsproduct having a gravity of 7.1API, and containing 4.1 percent by weightof sulfur and 23.7 percent by weight of heptaneinsoluble asphalts; atopped Middle East crude oil having a gravity of 110 API and containingabout 10.1 percent by weight of asphaltenes and 5.2 percent by weight ofsulfur; and, a vacuum residuum having a gravity of 8.8 API, containing3.0 percent by weight of sulfur and 4,300 p.p.m. of nitrogen.

The utilization of our invention affords the conversion of such materialinto distillable hydrocarbons, heretofore having been consideredvirtually impossible to achieve on a continuous basis with an acceptablecatalyst life. The principal difficulty, heretofore encountered in afixed-bed catalytic system, resides in the lack of sufficient stabilityin the presence of relatively large quantities of metals-Le. from about150 p.p.m. to as high as 750 p.p.m., computed as the element-andadditionally from the presence of large quantities of asphaltic materialand other nondistillables. The asphaltic material comprises highmolecular weight coke precursors, insoluble in light normally liquidhydrocarbons such as pentane and/or heptane. The asphaltic material isgenerally found to be dispersed within the black oil, and, whensubjected to elevated temperature, has the tendency to flocculate andpolymerize whereby the conversion thereof to more valuable oil-solubleproducts becomes extremely difficult.

OBJECTS AND EMBODIMENTS A principal object of our invention is to removeinsoluble asphaltenes from a hydrocarbonaceous charge stock. A corollaryobjective is to convert an asphaltene-free black oil into lower-boilinghydrocarbon products.

Another object is to provide a combination process for facilitating theconversion of asphaltic charge stocks by l initially removingasphaltenes and (2) thermally cracking the resulting substantiallyasphaltene-free hydrocarbonaceous material.

Therefore, in one embodiment, our invention provides a process foreffecting the removal of asphaltenes from a heavy hydrocarbonaceouscharge stock which comprises admixing said charge stock and hydrogen atsuperatmospheric pressure above about 1,000 p.s.i.g., depressuring theresulting mixture to a level below about 200 p.s.i.g. into an elongatedfoam chamber, removing an asphaltene-containing foam from the upperportion of said foam chamber and recovering a substantiallyasphaltene-free hydrocarbon fraction from the lower portion thereof.

In another embodiment, the asphaltene-free fraction is introduced into athermal cracking reaction zone, or coil, and lower-boiling hydrocarbonproducts are recovered from the resulting cracked product effluent.

Other embodiments of our invention are primarily directed towardparticular operating techniques and preferred ranges of operatingvariables and conditions. These, as well as other objects will beevident from the following, more detailed description of our invention.

SUMMARY OF INVENTION As hereinbefore set forth, our invention isprimarily directed toward the separation, or removal, of asphaltenesfrom a hydrocarbonaceous black oil. The encompassed process facilitatesasphaltene removal by providing a relatively simple and economicaloperating technique. The charge stock is initially admixed with hydrogenin an amount of from to about 1,000 scf./Bbl., and at a pressure in therange of from 1,000 to about 5,000 p.s.i.g. The minimum hydrogenrequirement is about 5.0 cubic feet per pound of asphaltenes. The mixingis effected at a temperature in the range of 250 F to about 700 F.

The high pressure oil/hydrogen mixture is throttled into a foam chamber,entering at a lower locus thereof. The specific design of the foamchamber does not constitute an essential element of our invention. Onesuitable scheme involves depressuring to a pressure of from 30 to about200 p.s.i.g. by discharging into the chamber through a sparger assembly.The pressure drop occurring across the sparger nozzles permits thedissolved hydrogen to come out of solution. The released hydrogen formsbubbles which nucleate at the large asphaltene molecules, therebycarrying the same to the upper foam section of the chamber. Nucleationof the hydrogen at the asphaltenes is facilitated when the elongatedfoam chamber is equipped with a turbine mixture which providesturbulence at the sparger nozzles.

Asphaltene-containing foam is continuously removed from the upperportion of the foam chamber as a result of being displaced by theincoming oil-hydrogen mixture. A substantially asphaltene-freehydrocarbon stream is withdrawn from a lower portion of the chamber. Theasphaltic foam is introduced into a suitable foam breaker, such as arotary vacuum filter. In the filter, for example, the foam is feddirectly into the feed pan, and is drawn up against the filter medium.This technique breaks the foam, the hydrogen being released into thedrum from which it may be recycled to the mixing zone. Although makeuphydrogen may be introduced at any convenient point of the process, apreferred locus is the hydrogen recycle line prior to the mixing zone.Asphaltenes collected on the drum are removed from the system. Wheredesired, the filter cake may be washed with a light hydrocarbon capableof dissolving residual, soluble distillables from the asphaltic sludge.Suitable hydrocarbons include heptane, hexane, cyclohexane, etc. Thisstream may be conveniently admixed with the distillable materialemanating from the lower portion of the foam chamber.

In another embodiment, the distillable material from the foam chamber,along with any residual distillables removed from the asphaltic sludge,is introduced into a thermal cracking reaction zone, or coil. Thecharge, with or without added hydrogen, is heated to a temperature aboveabout 800 F., preferably from about 825 F. to about l,000 F., and raisedto a pressure of from 300 to about 3,000 p.s.i.g. The thermally crackedproduct effluent is separated, for example in a vacuum column to providea distillable hydrocarbon product stream. Since some condensation of thehigher molecular weight is effected in the cracking zone, a heavyfraction is withdrawn from the separation zone and recycled to combinewith the fresh feed charge to the initial mixing zone.

DESCRIPTION OF DRAWING The accompanying drawing illustrates anembodiment of our invention wherein the asphaltene-free distillables aresubjected to thermal cracking. The embodiment is presented by way of asimplified flow diagram in which valves, pumps, heaters, compressors,startup lines, heat-recovery circuits, and other miscellaneousappurtenances have been omitted. The use of these, and other standardhardware, are well within the purview of one skilled in the art ofpetroleum refining techniques.

The drawing will be described in connection with the deasphalting andconversion of 40,000 BbL/day of a vacuum column bottoms product having agravity of about 100 AP! and containing about 10.0 percent by weight ofheptane-insoluble asphaltenes. The charge stock enters the process byway of line 1, and is admixed with a heavy recycle stream in line 3, themixture continuing through line 1 into mixing zone 5. Hydrogen,including makeup and recycled hydrogen from line 4, enters mixing zone 5through line 2. The temperature of the mixture is about 400 F and thepressure is about 1,000 p.s.i.g. The hydrogen circulation is about 5.0cubic feet per pound of asphaltenes, or about 440,000 scf./hr.

The mixture is introduced into foam chamber 7 via line 6, and isdepressured therein, through sparger nozzles, to a pressure slightlyless than about 100 p.s.i.g. Asphaltene-containing foam is withdrawnthrough line 8 into foam breaker 9, the latter being a rotary vacuumfilter. The asphaltic cake is removed by way of line 10, and hydrogen isrecirculated through line 4 by compressive means not illustrated.Asphalt is removed in an amount of 2,112,362 lbs/day, or slightly morethan 1,000 tons/day.

An asphaltene-free hydrocarbon stream is withdrawn from foam chamber 7through line 11 and, following heating to a temperature of about 900 F.,is introduced into thermal coil 12 at a pressure of 100 p.s.i.g. Thethermally cracked product effluent in line 13 is introduced into productseparation means 14. Distillable hydrocarbons, having an end boilingpoint of about l,050 F. are removed by way of line 15, in an amount ofabout 39,770 BbL/day. About 40,000 BbL/day of nonvacuum distillabletower bottoms is withdrawn by way of line 3, and recycled therethroughto mixing zone 5. In effect, this recycle provides a combined liquidfeed ratio to thermal coil 12 of 2.0, which value is within thepreferred range of 1.1 to 6.0.

The foregoing specification indicates the method by which our inventionis effected, and, with respect to one embodiment, the benefits affordedthrough the utilization thereof.

We claim as our invention:

1. A process for the removal of asphaltenes from a heavyhydrocarbonaceous charge stock which comprises admixing said chargestock and hydrogen at superatmospheric pressure above about 1,000p.s.i.g., depressuring the resulting mixture to a level below aboutp.s.i.g., into an elongated foam chamber, removing anasphaltene-containing foam from the upper portion of said foam chamberand recovering a substantially asphaltene-free hydrocarbon fraction fromthe lower portion thereof.

2. The process of claim 1 further characterized in that said chargestock and hydrogen are admixed at a pressure in the range of 1,000p.s.i.g., to about 5,000 p.s.i.g., and at a temperature of 250 F. toabout 700 F.

3. The process of claim 1 further characterized in that saidasphaltene-containing foam is introduced into a foam breaker, said foamis separated into an asphaltic residuum and a hydrogen-rich gaseousphase, and said gaseous phase is recycled to combine with said chargestock.

4. The process of claim 1 further characterized in that saidasphaltene-free fraction is introduced into a thermal cracking reactionzone, or coil, and lower-boiling hydrocarbon products are recovered fromthe resulting cracked product effluent.

S. The process of claim 4 further characterized in that said producteffluent is separated to recover lower-boiling hydrocarbon products andto provide a higher-boiling stream, the latter being recycled to combinewith said charge stock.

2. The process of claim 1 further characterized in that said chargestock and hydrogen are admixed at a pressure in the range of 1,000p.s.i.g., to about 5,000 p.s.i.g., and at a temperature of 250* F. toabout 700* F.
 3. The process of claim 1 further characterized in thatsaid asphaltene-containing foam is introduced into a foam breaker, saidfoam is separated into an asphaltic residuum and a hydrogen-rich gaseousphase, and said gaseous phase is recycled to combine with said chargestock.
 4. The process of claim 1 further characterized in that saidasphaltene-free fraction is introduced into a thermal cracking reactionzone, or coil, and lower-boiling hydrocarbon products are recovered fromthe resulting cracked product effluent.
 5. The process of claim 4further characterized in that said product effluent is separated torecover lower-boiling hydrocarbon products and to provide ahigher-boiling stream, the latter being recycled to combine with saidcharge stock.